You can't.
They need therapy and whoever they deal with has to be patient if they want to be with them. They won't ever get over it or forget.
As most things it takes time.
What is therapy supposed to do?
What if it affects the relationship?
The way this one girl would act in public, nikkas probably thought I was the abuser

its deep. Women and same sex relationships are going through this and they dont even know because nobody showed them this wheel or think its taboo.